U.S. patent application number 13/041802 was filed with the patent office on 2011-09-08 for salts of thiophosphoric acids and use thereof in lubricants.
This patent application is currently assigned to BASF SE. Invention is credited to Dirk GERHARD, Laszlo SZARVAS, Corvin VOLKHOLZ, Matthias VOLKHOLZ.
Application Number | 20110218130 13/041802 |
Document ID | / |
Family ID | 44531844 |
Filed Date | 2011-09-08 |
United States Patent
Application |
20110218130 |
Kind Code |
A1 |
SZARVAS; Laszlo ; et
al. |
September 8, 2011 |
SALTS OF THIOPHOSPHORIC ACIDS AND USE THEREOF IN LUBRICANTS
Abstract
Salts of the anion of di-, tri- or tetrathiophosphoric acid of
the formula I ##STR00001## in which Z.sup.1 and Z.sup.2 are each
independently an oxygen or sulfur atom, and R.sub.a and R.sub.b are
each independently an organic group having 1 to 20 carbon atoms,
and a cation which comprises a heterocyclic ring system having one
to three nitrogen atoms.
Inventors: |
SZARVAS; Laszlo;
(Ludwigshafen, DE) ; GERHARD; Dirk; (Mannheim,
DE) ; VOLKHOLZ; Matthias; (Erkelenz, DE) ;
VOLKHOLZ; Corvin; (Erkelenz, DE) |
Assignee: |
BASF SE
Ludwigshafen
DE
ILCO Chemikalien GmbH
Erkelenz
DE
|
Family ID: |
44531844 |
Appl. No.: |
13/041802 |
Filed: |
March 7, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61311412 |
Mar 8, 2010 |
|
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|
Current U.S.
Class: |
508/286 ;
548/335.1; 568/14 |
Current CPC
Class: |
C07D 233/58 20130101;
C07F 9/06 20130101; C10M 133/46 20130101 |
Class at
Publication: |
508/286 ;
548/335.1; 568/14 |
International
Class: |
C10M 133/46 20060101
C10M133/46; C07D 233/58 20060101 C07D233/58; C07F 9/06 20060101
C07F009/06 |
Claims
1. A salt of the anion of di-, tri- or tetrathiophosphoric acid of
the formula I ##STR00014## in which Z.sup.1 and Z.sup.2 are each
independently an oxygen or sulfur atom, and R.sub.a and R.sub.b are
each independently an organic group having 1 to 20 carbon atoms,
and a cation which comprises a heterocyclic ring system having one
to three nitrogen atoms.
2. A salt according to claim 1, wherein Z.sup.1 and Z.sup.2 in
formula I are each an oxygen atom.
3. A salt according to claim 1 or 2, wherein R.sub.a and R.sub.b in
formula I are each independently a C1 to C20 alkyl group.
4. A salt according to any of claims 1 to 3, wherein the sum of the
carbon atoms in the R.sub.a and R.sub.b radicals is 12 to 40.
5. A salt according to any of claims 1 to 4, wherein one of the
R.sub.a and R.sub.b radicals is, or both R.sub.a and R.sub.b
radicals are, a 2-propylheptyl group.
6. A salt according to any of claims 1 to 5, wherein the cation is
an imidazolium cation of the formula II ##STR00015## a pyridinium
cation of the formula III ##STR00016## a pyrazolium cation of the
formula IV ##STR00017## an imidazolinium cation of the formula V
##STR00018## or a triazolium cation of the formula VI ##STR00019##
where R and R1 to R5 are each independently a hydrogen atom or an
organic group having 1 to 20 carbon atoms.
7. A salt according to any of claims 1 to 6, wherein the cation is
an imidazolium cation of the formula II ##STR00020## where R and R1
are each independently an organic group having 1 to 20 carbon
atoms, and R2, R3 and R4 are each independently a hydrogen atom or
an organic group having 1 to 20 carbon atoms.
8. A process for preparing salts according to any of claims 1 to 7,
which comprises reacting the alkylcarbonate salt of the cation with
the appropriate di-, tri- or tetrathiophosphoric acid.
9. The use of the salts according to claims 1 to 7 or of
compositions comprising a salt according to any of claims 1 to 7 as
or in lubricants.
10. The use of the salts according to any of claims 1 to 7 or of
compositions comprising a salt according to any of claims 1 to 7 as
or in hydraulic fluids, damping fluids or force transmission
media.
11. A lubricant comprising a salt according to any of claims 1 to
7.
12. A lubricant comprising 0.1 to 20% by weight of the salts
according to any of claims 1 to 7.
13. The lubricant according to claim 11 or 12, which is a
room-temperature liquid lubricant (lubricant oil) which consists to
an extent of more than 50% by weight of at least one animal oil,
vegetable oils, mineral oils or synthetic oil or mixtures
thereof.
14. A hydraulic fluid, damping fluid or force transmission medium
comprising a salt according to any of claims 1 to 7.
15. A composition which comprises a salt according to any of claims
1 to 7 and consists of ionic liquids to a total extent of at least
20% by weight.
16. A composition which comprises a salt according to any of claims
1 to 7 and consists of ionic liquids to a total extent of at least
50% by weight.
17. The use of compositions according to claim 15 or 16 as a
lubricant, hydraulic fluid, damping fluid or force transmission
medium.
18. A di-, tri- or tetrathiophosphoric acid of the formula VII
##STR00021## in which Z.sup.1 and Z.sup.2 are each independently an
oxygen or sulfur atom, the R.sub.a radical is a 2-propylheptyl
group and R.sub.b radical is an organic group having 1 to 20 carbon
atoms.
Description
[0001] The invention relates to salts of the anion of di-, tri- or
tetrathiophosphoric acid of the formula I
##STR00002##
in which Z.sup.1 and Z.sup.2 are each independently an oxygen or
sulfur atom, and R.sub.a and R.sub.b are each independently an
organic group having 1 to 20 carbon atoms, and a cation which
comprises a heterocyclic ring system having one to three nitrogen
atoms, and to the use of these salts in lubricants.
[0002] During the use of lubricants or hydraulic fluids, there is
damage to the apparatus parts over the course of time. The damage
is attributable especially to corrosion and abrasion on metal parts
or wear of the metal parts.
[0003] The addition of suitable additives to lubricants, especially
lubricant oils, or hydraulic fluids is intended to counteract such
damage over a maximum period.
[0004] The use of metal salts of dithiophosphoric acid, especially
zinc dithiophosphates, is known as such an additive. However, a
disadvantage is that metal salts, especially metal oxides such as
zinc oxide, form as residues during the use of such metal salts,
for example in internal combustion engines. Such metal oxides form
deposits on apparatus parts or pollute the environment in the form
of fine dust.
[0005] Additives which burn very substantially without residue,
which is also referred to as ashlessness, are therefore
desired.
[0006] Salts of dithiophosphoric acid with organic cations are
known from DE-A 2131926 and DE-A 2221646. Replacement of the metal
salts by such organic cations is intended to achieve
ashlessness.
[0007] DE-A 2131926 describes salts of a phosphonium cation and a
thiophosphoric acid derivative as additives to hydraulic fluid. The
salts described prevent damage to metal parts of the hydraulic
system. Such damage is attributed to a wear effect of the hydraulic
fluid.
[0008] DE-A 2221646 discloses lubricant oils which comprise amine
salts of a thiophosphoric acid. The amine salts reduce the abrasion
on plant parts. The amine cation is a quaternary ammonium
cation.
[0009] For use in lubricant oils, there is a constant search for
improved additives which even better meet very substantially all
above demands.
[0010] It was therefore an object of the present invention to find
additives, for example to lubricants or hydraulic fluids, which are
easy to prepare or to obtain, have good compatibility with
different lubricant oils and can therefore be used in a wide
variety of different lubricants or hydraulic fluids, have very good
action and significantly reduce corrosion and abrasion on metal
parts, and do not form any residues, i.e. are ashless.
[0011] Accordingly, the salts of the formula I and the use thereof
in lubricant oils have been found.
[0012] The inventive salts are salts of the anion of di-, tri- or
tetrathiophosphoric acid of the formula I
##STR00003##
in which Z.sup.1 and Z.sup.2 are each independently an oxygen or
sulfur atom, and R.sub.a and R.sub.b are each independently an
organic group having 1 to 20 carbon atoms, and a cation which
comprises a heterocyclic ring system having one to three nitrogen
atoms.
The Anion
[0013] Preferably, both Z.sup.1 and Z.sup.2 in formula I are an
oxygen atom. The anion is therefore preferably that of a
dithiophosphoric acid.
[0014] R.sub.a and R.sub.b in formula I are preferably each an
organic group having 1 to 16 carbon atoms, more preferably 6 to 16
carbon atoms, where the organic group may also comprise
heteroatoms, e.g. oxygen or nitrogen, preferably in the form of a
hydroxyl group, ether group, or primary, secondary or tertiary
amino group.
[0015] More particularly, R.sub.a and R.sub.b in formula I are each
an organic group which consists exclusively of carbon and hydrogen
and does not comprise any other heteroatoms, i.e. are each a
hydrocarbon group. This may be an aliphatic or aromatic hydrocarbon
group, but may also be a hydrocarbon group which consists both of
aliphatic and of aromatic groups.
[0016] R.sub.a and R.sub.b are more preferably each independently a
C1 to C20 alkyl group, especially a C1 to C16, even more preferably
a C6 to C16 alkyl group and, in a particular embodiment, a C8 to
C12 alkyl group.
[0017] The parent dithiophosphoric acid of the anion is obtainable
in a known manner by reacting phosphorus sulfides such as
P.sub.4S.sub.10 or P.sub.2S.sub.5 with the corresponding alcohols
of the R.sub.a and R.sub.b radicals. In this reaction, it is
possible to use a single alcohol or else, of course, a mixture of
alcohols. In the case of use of a single alcohol, R.sub.a and
R.sub.b are identical. In contrast, in the case of use of an
alcohol mixture, depending on the compositions of the alcohol
mixture, mixtures of compounds with a corresponding random
distribution of identical and different R.sub.a and R.sub.b
radicals are obtained.
[0018] Irrespective of whether R.sub.a and R.sub.b in the anion of
the formula I, as a result of the preparation of the
dithiophosphoric acid, are identical or different, the sum of the
carbon atoms in the R.sub.a and R.sub.b radicals in a preferred
embodiment is 12 to 40, more preferably 14 to 30 and most
preferably 16 to 24.
[0019] More particularly, R.sub.a and R.sub.b are identical by
virtue of the use of a single alcohol in the preparation of the
dithiophosphoric acid.
[0020] Particularly suitable anions of the formula I include anions
in which at least one of the R.sub.a and R.sub.b radicals is a
2-ethylhexyl group or a 2-propylheptyl group; very particularly
suitable are the anions, in which both R.sub.a and R.sub.b radicals
are a 2-ethylhexyl group or both R.sub.a and R.sub.b radicals are a
2-propylheptyl group (see formulas in the examples)
The Cation
[0021] Preference is given to a cation which comprises a
heterocyclic ring system having one, two or three nitrogen atoms as
part of the ring system.
[0022] Useful cations of this kind include monocyclic, bicyclic,
aromatic or nonaromatic ring systems. Examples include bicyclic
systems, as described in WO 2008/043837. The bicyclic systems of WO
2008/043837 are diazabicyclo derivatives, preferably composed of a
7-membered ring and a 6-membered ring, which comprise an amidinium
group; a particular example is the
1,8-diazabicyclo[5.4.0]undec-7-enium cation.
[0023] Very particular preference is given to a cation with a five-
or six-membered heterocyclic ring system with one, two or three
nitrogen atoms as part of the ring system.
[0024] Useful organic cations of this kind include, for example
pyridinium cations, pyridazinium cations, pyrimidinium cations,
pyrazinium cations, imidazolium cations, pyrazolium cations,
pyrazolinium cations, imidazolinium cations, thiazolium cations,
triazolium cations, pyrrolidinium cations and imidazolidinium
cations. These cations are detailed, for example in WO 2005/113702.
If necessary for a positive charge on the nitrogen atom or in the
aromatic ring system, the nitrogen atoms each bear a hydrogen atom
or an organic group having generally not more than 20 carbon atoms,
preferably an optionally substituted saturated or unsaturated
hydrocarbon group, especially a C1 to C16 alkyl group or alkenyl
group, especially a C1 to C10, and more preferably a C1 to C4 alkyl
group, as substituents; the above hydrocarbon groups or alkyl
groups or alkenyl groups may be substituted by functional groups,
for example a hydroxyl group.
[0025] The carbon atoms of the ring system may also be substituted
by organic groups having generally not more than 20 carbon atoms,
preferably a hydrocarbon group, especially a C1 to C16 alkyl group
or alkenyl group, especially a C1 to C10 and more preferably a C1
to C4 alkyl group; the above hydrocarbon groups or alkyl groups or
alkenyl groups may in turn be substituted by functional groups, for
example a hydroxyl group.
[0026] The cation is more preferably an imidazolium cation of the
formula II
##STR00004##
a pyridinium cation of the formula III
##STR00005##
a pyrazolium cation of the formula IV
##STR00006##
an imidazolinium cation of the formula V
##STR00007##
or a triazolium cation of the formula VI
##STR00008##
where R and R1 to R5 are each independently a hydrogen atom or an
organic group having 1 to 20 carbon atoms.
[0027] In the imidazolium cations of the formula II, R and R1 are
preferably each independently an organic group having 1 to 20
carbon atoms, especially having 1 to 12 carbon atoms. The organic
group is preferably a hydrocarbon group with no further
heteroatoms; R and R1 are especially each independently a C1 to C20
alkyl group, more preferably a C1 to C12 alkyl group, most
preferably a C1 to C4 alkyl group.
[0028] The R2 to R4 radicals in formula II are each independently a
hydrogen atom or an organic group having 1 to 20 carbon atoms,
especially 1 to 12 carbon atoms; in the case of an organic group as
a radical, preference is given in turn to a hydrocarbon group with
no further heteroatoms, especially a C1 to C20 alkyl group, more
preferably a C1 to C12 alkyl group, most preferably a C1 to C4
alkyl group. The R2 to R4 radicals in formula II are more
preferably a hydrogen atom or a C1 to C4 alkyl group. The R2 to R4
radicals in formula II are most preferably a hydrogen atom.
[0029] In the pyridinium cations of the formula III, R is
preferably an organic group having 1 to 20 carbon atoms, especially
having 1 to 12 carbon atoms. The organic group is preferably a
hydrocarbon group with no further heteroatoms; R is preferably a C1
to C20 alkyl group, more preferably a C1 to C12 alkyl group, most
preferably a C1 to C4 alkyl group.
[0030] The R1 to R5 radicals in formula III are each independently
a hydrogen atom or an organic group having 1 to 20 carbon atoms,
especially 1 to 12 carbon atoms; in the case of an organic group as
a radical, preference is given in turn to a hydrocarbon group with
no further heteroatoms, especially a C1 to C20 alkyl group, more
preferably a C1 to C12 alkyl group, most preferably a C1 to C4
alkyl group. The R1 to R5 radicals in formula III are more
preferably a hydrogen atom or a C1 to C4 alkyl group. The R1 to R5
radicals in formula III are most preferably a hydrogen atom.
[0031] In the pyrazolium cations of the formula IV, R and R1 are
preferably each an organic group having 1 to 20 carbon atoms,
especially having 1 to 12 carbon atoms. The organic group is
preferably a hydrocarbon group with no further heteroatoms; R and
R1 are especially each independently a C1 to C20 alkyl group, more
preferably a C1 to C12 alkyl group, most preferably a C1 to C4
alkyl group.
[0032] The R2 to R4 radicals in formula IV are each independently a
hydrogen atom or an organic group having 1 to 20 carbon atoms,
especially 1 to 12 carbon atoms; in the case of an organic group as
a radical, preference is given in turn to a hydrocarbon group with
no further heteroatoms, especially a C1 to C20 alkyl group, more
preferably a C1 to C12 alkyl group, most preferably a C1 to C4
alkyl group. The R2 to R4 radicals in formula IV are more
preferably a hydrogen atom or a C1 to C4 alkyl group. The R2 to R4
radicals in formula IV are most preferably a hydrogen atom.
[0033] In the imidazolinium cations of the formula V, R, R1 and R2
are preferably each a hydrogen atom or an organic group having 1 to
20 carbon atoms, especially having 1 to 18 carbon atoms; in the
case of an organic group as a radical, the group is preferably a
saturated or unsaturated hydrocarbon group which may optionally be
substituted by one or more functional groups, for example a
hydroxyl group.
[0034] Particularly preferred imidazolinium cations of the formula
V are those in which one of the R or R1 radicals is a hydrogen atom
and the other R or R1 radical is a C1 to C8 alkyl group or a C1 to
C8 hydroxyalkyl group. R2 may especially be a saturated or
unsaturated hydrocarbon radical, e.g. a C1 to C20 alkyl group or a
C2 to C20 alkylene group.
[0035] One example of such an imidazolinium cation is the cation
of
Amine-O (BASF trade name) of the formula
##STR00009##
[0036] The cation or salt is obtainable therefrom by addition of
the corresponding acid and associated addition of a hydrogen atom
as the R radical onto the unsubstituted nitrogen atom.
[0037] In the triazolium cations of the formula VI, R and R1 are
preferably each a hydrogen atom or an organic group having 1 to 20
carbon atoms, especially having 1 to 18 carbon atoms; in the case
of an organic group as a radical, preference is given in turn to a
hydrocarbon group with no further heteroatoms, especially a C1 to
C20 alkyl group, more preferably a C1 to C12 alkyl group, most
preferably a C1 to C4 alkyl group. The R and R1 radicals in formula
VI are more preferably each a hydrogen atom or a C1 to C4 alkyl
group.
[0038] The R2 and R3 radicals in formula VI are preferably each
independently a hydrogen atom or an organic group having 1 to 20
carbon atoms, where the R2 and R3 radicals may also be joined to
one another to form a ring system. R2 and R3 may, for example, each
independently be a hydrogen atom or an organic group having 1 to 12
carbon atoms, in the case of an organic group as a radical, the
group is preferably a hydrocarbon group with no further
heteroatoms, especially a C1 to C20 alkyl group, more preferably a
C1 to C12 alkyl group, most preferably a C1 to C4 alkyl group. The
R2 and R3 radicals together may more preferably form a benzene
ring, where the carbon atoms of the benzene ring may in turn
optionally be substituted by organic groups, for example organic
groups having 1 to 10 carbon atoms, especially C1 to C10 alkyl
groups, more preferably C1 to C4 alkyl groups.
[0039] A preferred triazolium cation is, for example the cation of
benzotriazole, which in turn by reaction with the desired acid and
addition of a hydrogen atom as the R radical onto the corresponding
nitrogen atom, as shown in formula VI.
##STR00010##
[0040] The cation is most preferably an imidazolium cation of the
above formula II, where R and R1 are each independently an organic
group having 1 to 20 carbon atoms, and R2, R3 and R4 are each
independently a hydrogen atom or an organic group having 1 to 20
carbon atoms. With regard to the preferred organic groups, the
above statements apply; more particularly, the organic groups are
C1 to C12, especially C1 to C4, alkyl groups.
[0041] Examples of particularly preferred imidazolium cations
include:
1-methyl-3-methylimidazolium (R and R1=methyl, R2, R3, R4=H), MMIM
for short 1-ethyl-3-methylimidazolium (R=ethyl and R1=methyl, R2,
R3, R4=H), EMIM for short 1-ethyl-3-ethylimidazolium (R and
R1=ethyl, R2, R3, R4=H), EEIM for short 1-butyl-3-methylimidazolium
(R=butyl and R1=methyl, R2, R3, R4=H), BMIM for short
1-butyl-3-ethylimidazolium (R=butyl and R1=ethyl, R2, R3, R4=H),
BEIM for short 1-butyl-3-butylimidazolium (R and R1=butyl, R2, R3,
R4=H), BBIM for short 1-octyl-3-methylimidazolium (R=octyl and
R1=methyl, R2, R3, R4=H), OMIM for short
Preparation of the Salts
[0042] The inventive salts can be prepared by various known
methods.
[0043] More particularly, the inventive salts can be prepared from
other salts of the cation, for example from the alkylcarbonate
salts or hydroxide salts.
[0044] Salts of the abovementioned cations and an alkylcarbonate as
the anion, and the preparation of such salts, are known, for
example from WO 2005/021484. This WO also describes the conversion
of the alkylcarbonate salts to salts of other anions by addition of
an acid.
[0045] According to the teaching of WO, imidazolium alkylcarbonates
or the alkylcarbonates of other cations (also referred to
hereinafter collectively as alkylcarbonate for short) can be
converted to salts of the formula I by addition of the di-, tri- or
tetrathiophosphoric acid. The reaction forms carbon dioxide.
[0046] The preferred starting compound is the imidazolium
methylcarbonate as the starting material.
[0047] The di-, tri- or tetrathiophosphoric acid selected is the
corresponding acid with the desired R.sub.a and R.sub.b radicals.
Di-, tri- or tetrathiophosphoric acids of the formula VII
##STR00011##
in which Z.sup.1 and Z.sup.2 are each independently an oxygen or
sulfur atom, the R.sub.a radical is a 2-propylheptyl group and
R.sub.b radical is an organic group having 1 to 20 carbon atoms,
have not been described to date and, in the context of this
invention, are some of the preferred phosphoric acids, especially
in the form of dithiophosphoric acid (Z.sup.1 and Z.sup.2 are each
oxygen) for preparation of the above salts. More preferably, both
R.sub.a and R.sub.b radicals in formula VII are a 2-propylheptyl
group. Preferred salts are salts with cations of formulas II to VI,
in particular with an imidazolium cation of formula II, and the
anion of formula VII.
[0048] The alkylcarbonate can be reacted with the di-, tri- or
tetrathiophosphoric acid, for example, at 0 to 100.degree. C.,
especially 10 to 80.degree. C. and standard pressure, optionally in
the presence of a solvent.
[0049] Suitable solvents are especially alcohols such as methanol,
ethanol, isopropanol. Particular preference is given to methanol as
solvent.
[0050] The alkylcarbonate and the di-, tri- or tetrathiophosphoric
acid can each be used in excess. Preference is given to a molar
ratio of 1:0.8 to 0.8:1.
[0051] Very particular preference is given to using the
alkylcarbonate and the di-, tri- or tetrathiophosphoric acid in an
approximately stoichiometric ratio.
[0052] Alternatively, the compounds of the formula I can also be
prepared the to the hydroxide salt of the abovementioned cations.
Here, the reaction with the di-, tri- or tetrathiophosphoric acid
is effected with elimination of water.
[0053] In addition, to prepare the inventive salts, any desired
metathesis reactions, i.e. anion exchange reactions, are possible,
proceeding from any desired salt of an abovementioned cation and
exchange of the anion for the corresponding anion of the di-, tri-
or tetrathiophosphoric acid. Generally, undesired starting salts
for the anion exchange are halides and especially chlorides, in
view of the later use and of a possible residual content of
chloride.
[0054] The inventive salts comprise preferably less than 100 pm,
especially less than 20 ppm, of halides. They are more preferably
free of halides.
[0055] Preferred salts are for example,
MMIM bis-2-ethylhexyldithiophosphate=MMIM [(2EH).sub.2DTP] MMIM
bis-2-propylheptyldithiophosphate=MMIM [(2PH).sub.2DTP] EMIM
bis-2-ethylhexyldithiophosphate=EMIM [(2EH).sub.2DTP] EMIM
bis-2-propylheptyldithiophosphate=EMIM [(2PH).sub.2DTP] EEIM
bis-2-ethylhexyldithiophosphate=EEIM [(2EH).sub.2DTP] EEIM
bis-2-propylheptyldithiophosphate=EEIM [(2PH).sub.2DTP] BMIM
bis-2-ethylhexyldithiophosphate=BMIM [(2EH).sub.2DTP] BMIM
bis-2-propylheptyldithiophosphate=BMIM [(2PH).sub.2DTP] BEIM
bis-2-ethylhexyldithiophosphate=BEIM [(2EH).sub.2DTP] BEIM
bis-2-propylheptyldithiophosphate=BEIM [(2PH).sub.2DTP] BBIM
bis-2-ethylhexyldithiophosphate=BBIM [(2EH).sub.2DTP] BBIM
bis-2-propylheptyldithiophosphate=BBIM [(2PH).sub.2DTP] OMIM
bis-2-ethylhexyldithiophosphate=OMIM [(2EH).sub.2DTP] OMIM
bis-2-propylheptyldithiophosphate=OMIM [(2PH).sub.2DTP] and
mixtures of the formula [cation] [(2EH).sub.x(2PH).sub.yDTP] where
x+y=2.
[0056] In addition, it is also possible to use other mixtures.
[0057] The salt of the formula I is preferably an ionic liquid,
i.e. the salt has a melting point of less than 100.degree. C.,
often even less than 20.degree. C. After removal of the solvent,
the salts can therefore be transported, stored and used in a simple
manner, in the form of liquids.
Use
[0058] The inventive salts or compositions which comprise an
inventive salt are suitable as lubricants. In this context, a
lubricant is understood to mean any substance which is used to
prevent or to reduce frictional influences between surfaces moving
relative to one another.
[0059] More particularly, the inventive salts are suitable as
additives to customary lubricants, whether they be liquid
lubricants (lubricant oils), solid lubricants, pastes or greases
under standard conditions (20.degree. C., 1 bar).
[0060] Solid lubricants are, for example, low-friction coatings,
graphite, metal sulfides such as molybdenum sulfide or metal oxides
(TiO.sub.2, ZnO, inter alia).
[0061] Typical lubricant oils are compositions which comprise, as a
main constituent, an oil or mixture of oils and optionally also
further additives, or consist exclusively of an oil or mixture of
oils.
[0062] In a particular embodiment, the lubricants are lubricant
oils which consist to an extent of more than 50% by weight of at
least one animal oil, vegetable oils, mineral oils or synthetic
oil, or mixtures thereof.
[0063] Suitable oils are animal or vegetable oils or mineral oils;
they may also be synthetic oils which can be prepared from a wide
variety of different starting compounds, especially also from the
above animal, vegetable oils or mineral oils.
[0064] The oils, for example mineral oils, may be acyclic and/or
cyclic, saturated and/or unsaturated hydrocarbons which may
optionally comprise one or more heteroatoms, for example O, F, P,
N, S.
[0065] Examples of oils without heteroatoms include alkylbenzenes,
cycloalkanes, polyalphaolefins and copolymers of unsaturated
hydrocarbons; oils which comprise oxygen as a heteroatom include
alcohols, esters, ketones, furans, polyethers and copolymers of
olefins and, for example, acrylates, maleates or fumarates; oils
which comprise fluorine and oxygen as heteroatoms include perfluoro
ethers or esters; oils which comprise phosphorus and oxygen as
heteroatoms include phosphoric esters; oils, which comprise
phosphorus and nitrogen as heteroatoms include phosphazenes; oils
which comprise sulfur or nitrogen as heteroatoms, include
thiophenes.
[0066] The compounds mentioned are preferably liquid within the
temperature range of application, which may be in the range from
-80.degree. C. to +450.degree. C. (1013 mbar), but need not
necessarily be a liquid in the case of particular requirements
(e.g. low-friction coatings). The lubricant oils comprise the oils,
for example, in an amount of 1 to 99.9% by weight. The compositions
or lubricant oils may comprise additives if required, which
fulfill, for example, the following tasks: aging protection, wear
protection, extreme pressure additives, corrosion protection,
detergents, dispersants, demulsification, emulsification,
antifoams, and further tasks described in the literature (see also
in "Lubricant additives: chemistry and applications/editor Leslie
R. Rudnick, --2nd edition, 2009, CRC Press").
[0067] Animal or vegetable oils are, for example, rapeseed oil,
castor oil or fish oil.
[0068] Useful mineral oils include, for example, mineral oil
fractions from spindle oils up to SAE 30, 40 or 50 lubricant
oils.
[0069] Synthetic oils are especially oils which are obtainable by
esterifying or etherifying suitable starting materials, for example
including the aforementioned animal or vegetable oils or mineral
oils. Examples include diesters, as obtainable by esterification of
dicarboxylic acids such as adipic acid or sebacic acid with
monohydric alcohols, or oligoesters, which are obtainable by
esterification of mixtures of di- or oligocarboxylic acids, di- or
oligoalcohols and monoalcohols, for example oligoesters of sebacic
acid or adipic acid, a polyglycol and a monohydric alcohol such as
2-ethylhexanol.
[0070] Synthetic oils are, for example, oligomers which are liquid
even under standard conditions, (20.degree. C., 1 bar) and are
obtainable by polymerization, whether by free-radical
polymerization, polycondensation or other polyadduct formation, of
monomers. Useful examples are oligomers based on ethylene oxide,
propylene oxide, alkenes or isoalkenes, such as polyethylene
glycols, polypropylene glycols, polyisobutylenes, or polymers and
copolymers obtainable by free-radical polymerization of
ethylenically unsaturated monomers, for example based on vinyl
ethers, vinyl esters, acrylic esters, meteates, fumarates, etc.
[0071] The lubricants, or lubricant oils, find use, for example, as
motor oils (gasoline and diesel engines), transmission oils, chain
lubricants or lubricant greases. The list is only intended to
indicate customary uses of lubricants by way of example.
[0072] In addition, the inventive salts or compositions which
comprise an inventive salt are suitable as or in hydraulic fluids,
damping fluids or force transmission media.
[0073] The inventive salts are suitable as an additive for
compositions which are used in applications in which there is, or
there is a risk of, corrosion and abrasion on apparatus parts.
[0074] It is also possible to use mixtures of the inventive salts
as additives.
[0075] The compositions which are used, for example, as lubricants,
or lubricant oils, hydraulic fluids, damping fluids or force
transmission media preferably comprise at least 0.1% by weight,
more preferably at least 0.2% by weight, of the inventive salts,
whether it be only one inventive salt or a mixture of two or more
inventive salts. In general, a maximum content of 20% by weight,
especially of 10% by weight, or especially 5% by weight or more
preferably of 3% by weight is sufficient.
[0076] It should be noted that, in all above uses, aqueous systems
are also useful, especially biphasic systems composed of an aqueous
phase and a nonaqueous phase, in which the salt of the di-, tri- or
tetrathiophosphoric acid is preferably present in the nonaqueous
phase.
[0077] Lubricants may especially have a content of 0.1 to 20% by
weight, more preferably of 0.2 to 10% by weight, most preferably of
0.3 to 5% by weight, of the inventive salts.
[0078] Preferred inventive salts are ionic liquids (see above); for
this reason, they can also be used directly themselves as a
lubricant oil, hydraulic medium, damping fluid or other force
transmission media.
[0079] The inventive salts can also be mixed with other ionic
liquids or dissolved therein. Other ionic liquids include salts of
the above cations, for example of the pyridinium cations,
pyrazolium cations or especially of the imidazolium cations of the
formulae II, III and IV with any anions. Examples of such anions
include chloride, bromide, hydrogensulfate, tetrachloroaluminate,
thiocyanate, dicyanamide, methylsulfate, ethylsulfate,
methanesulfonate, formate, acetate, dimethylphosphate,
diethylphosphate, p-tolylsulfonate, tetrafluoroborate and
hexafluorophosphate, methylmethylphosphonate and
methylphosphonate.
[0080] The invention therefore also relates to compositions which
consist of ionic liquids to an extent of at least 20% by weight,
especially to an extent of at least 50% by weight and more
preferably to an extent of at least 70% by weight, and comprise
inventive salts, preferably in an amount of at least 0.1% by
weight, especially at least 0.5% by weight, most preferably in an
amount of at least 1% by weight, based on the composition.
[0081] The inventive salt may be dissolved in the ionic liquid; the
preferred maximum content then corresponds to that mentioned above
of 20% by weight.
[0082] More particularly, the inventive salt in these compositions
is itself an ionic liquid. In this case, the content thereof in the
mixture with other ionic liquids may be as high as desired and may
be up to 100% by weight; such compositions may, for example, also
consist of inventive salts to an extent of 0.1 to 90% by weight,
especially 0.5 to 50% by weight, of 10 to 99.9% by weight,
especially 50 to 99.5% by weight, of other ionic liquids, and
optionally 0 to 70% by weight, especially 0 to 50% by weight, of
further additives or solvents where the total content of ionic
liquids in the composition is preferably at least 20% by weight,
more preferably at least 50% by weight.
[0083] The above compositions which consist of ionic liquids to an
extent of at least 20% by weight are also correspondingly suitable,
with the same advantages already detailed above, as a lubricant
oil, hydraulic fluid, damping fluid or other force transmission
medium.
[0084] In summary, it can be stated that, when the inventive salts
composed of the anion of the di-, tri- or tetrathiophosphoric acid
are employed in the above uses, for example in lubricant oils, the
following advantages arise: [0085] better protection against wear
on plant parts (antiwear performance) [0086] a high level of
protection against oxidation of the oils [0087] promotion of the
action of other additives, e.g. phosphoric esters (synergistic
action) [0088] a relatively low content of sulfur and phosphorus in
the formulation [0089] ashlessness, i.e. there is no emission of
fine metal oxide dusts, as observed in the case of use of metal
salts in internal combustion engines of all types, for example
gasoline and diesel engines. This results in better environmental
compatibility, and [0090] an improvement in the frictional behavior
compared to conventional antiwear additives, which also leads, for
example, to a longer lifetime and to saving of energy.
[0091] The above effects can be achieved even at a low content of
the inventive salts in the compositions. Suitable compositions,
especially those for the above uses, comprise preferably not more
than 0.15 mol of phosphorus and 0.25 mol of sulfur and more
preferably not more than 0.1 mol of phosphorus and 0.2 mol of
sulfur per kg of composition; they preferably comprise at least
0.01 mol of phosphorus, more preferably at least 0.05 mol of
phosphorus and at least 0.01 mol of sulfur and more preferably at
least 0.05 mol of sulfur, where all molar amounts are based on 1
kilogram (kg) of composition, for example lubricants.
[0092] The salts of the invention can replace metal salts in
particular zinc salts, for example zinc dithiophosphates,
completely. Therefore, in a preferred embodiment of the invention,
the compositions, lubricant, lubricant oil, hydraulic fluid,
damping fluid and force transmission fluids comprise less than 0.2%
by weight, more preferred less than 0.1%, and most preferred less
than 0.05% by weight of zinc cations. In a very particular
preferred embodiment of the invention they are free of zinc
cations.
EXAMPLES
Preparation
Preparation of Inventive Imidazolium Dithiophosphates
[0093] A 1,3-dialkylimidazolium methylcarbonate dissolved in
methanol was initially charged and admixed dropwise with
dialkyldithiophosphoric acid in an approximately stoichiometric
ratio at 50.degree. C. while stirring. In the course of this there
was significant evolution of gas. After the end of addition, the
reaction mixture was stirred at 50.degree. C. for another hour. The
solvent was removed under reduced pressure and elevated
temperature, and the product was obtained as a pure substance.
[0094] The 1,3 dialkylimidazolium methylcarbonates used were:
EMIM methylcarbonate OMIM methylcarbonate
[0095] The dialkyldithiophosphoric acids used were:
di-2-ethylhexyldithiophosphoric acid (Deophos.RTM., D.O.G. Hamburg)
di-2-propylheptyldithiophosphoric acid
##STR00012##
[0096] The reaction proceeds by the following mechanism, shown
using the example of di-2-ethylhexyldithiophosphoric acid and of
EMIM methylcarbonate:
##STR00013##
Preparation Example 1
Preparation of EMIM di-2-ethylhexyldithiophosphate [EMIM]
[2EHDTP]
[0097] 155 g of EMIM methylcarbonate solution (46.6 g=0.25 mol of
EMIM methylcarbonate in methanol) were initially charged, and 90.4
g=0.255 mol of Deophos were slowly added dropwise at 50.degree. C.
while stirring. The reaction starts up immediately, and CO.sub.2
escapes.
[0098] After the end of addition, the mixture was stirred at
50.degree. C. for about another 1 h, until no further gas evolution
was visible.
[0099] The product was concentrated to dryness on a rotary
evaporator.
[0100] Final weight 118.9 g
[0101] The NMR data and elemental analysis agreed with EMIM
di-2-ethylhexyldithiophosphate.
Preparation Example 2
Preparation of OMIM di-2-ethylhexyldithiophosphate [OMIM]
[2EHDTP]
[0102] 162.4 g of OMIM methylcarbonate solution (53.6 g=0.2 mol of
OMIM in methanol) were initially charged, and 70.9 g (0.2 mol) of
Deophos were slowly added dropwise at 50.degree. C. while stirring.
In the course of this, CO.sub.2 escapes. After the end of addition,
the mixture was stirred at 50.degree. C. for about another 1 h
until no further gas evolution was visible.
[0103] The product was concentrated to dryness on a rotary
evaporator.
[0104] Final weight 109.7 g of yellow, high-viscosity liquid
[0105] The NMR data and elemental analysis agreed with OMIM
di-2-ethylhexyldithiophosphate.
Preparation Example 3
Preparation of di(2-propylheptyl)dithiophosphoric acid
[0106] 0.2 mol of diphosphorus pentasulfide (44 g) was suspended in
300 ml of toluene and heated to 75.degree. C. Then 0.8 mol of
2-propylheptanol (127 g) was added dropwise with evolution of gas
over a period of 1 h. The reaction mixture was stirred at
75.degree. C. for a further 2 hours. A clear solution was obtained.
The conversion was >95% (determined by means of acid-base
titration).
Performance Tests:
Load Carrying Capacity
[0107] The load carrying capacity was determined analogously to
ASTM D 5706 (staged test).
[0108] In the vibration-friction-wear instrument, abbreviated to
SRV instrument in German (Optimol Instruments, Munich) the
composition to be tested is applied to a disk and a ball is pressed
onto it with a defined, rising load, the composition serving as the
lubricant between plate and ball. The load is increased stepwise
until a coefficient of friction of 0.25 is exceeded.
[0109] Conditions: distance 1 mm, frequency 50 hertz, temperature:
room temperature, ball-disk specimen geometry, test load:
running-in time: 50 N-30 sec, then rising in 100 N steps until the
coefficient of friction is >0.25.
[0110] The measurements are stopped automatically as soon as it is
clear that the coefficient of friction begins to jump to a high
value, i.e. on commencement of damage to the disk or ball owing to
the lack of action of the composition as a lubricant. The load
applied on stoppage (in force per unit area, N/mm.sup.2) is
referred to as OK load; the higher the OK load, the better the
lubricity.
Oxidation Behavior
[0111] To determine the oxidation behavior, a DSC analysis was
performed under air. The composition was introduced into a glass
vessel and the temperature was increased from 30.degree. C. to
410.degree. C., and the amount of heat released by oxidation
(exothermic reaction) was determined. The higher the amount of
heat, the more intensive the oxidation. The lower the measured
amount of heat, the better is the oxidation behaviour.
[0112] The lubricant oils (base oils) used were products customary
on the market, such as DITA, Palatinol 10P, Synative ES TMTC.
[0113] For comparison, the additive used was the zinc salt
customary on the market zinc (di-2-ethylhexyldithiophosphate).sub.2
(=Zn [2EHDTP]2); owing to the divalency of zinc, the zinc salts
comprise two dithiophosphate anions.
Load Carrying Capacity
TABLE-US-00001 [0114] OK load Additive N/mm.sup.2 [% by wt.]
Additive DITA (diisotridecyl 100% 1130 adipate) DITA 99.50% 2000
0.50% EMIM 2EHDTP DITA 98.26% 2080 1.74% OMIM 2EHDTP DITA 98.10%
2320 1.90% EMIM 2EHDTP DITA 98.92% 1300 1.08% Zn[(2EHDTP)]2 OTHER
BASE OILS 100% 1140 Palatinol 10P (BASF) Synative ES TMTC 100% 1190
(Cognis) trimethylolpropane C8-C10 ester Oxidation behavior
(DSC)
TABLE-US-00002 Evolution of heat as a result of oxidation Additive
[mJ] [% by wt.] Additive DITA 100% 4166 DITA 99.50% 2531 0.50% EMIM
2EHDTP DITA 98.26% 1208 1.74% OMIM 2EHDTP DITA 98.10% 101 1.90%
EMIM 2EHDTP DITA 98.92% 1870 1.08% Zn [(2EHDTP)]2 Combined systems:
synergism with aryl phosphates, tert-butylated.
TABLE-US-00003 Evolution of heat OK load as a result of
[N/mm.sup.2] oxidation [mJ] DITA 98.03% Aryl phosphate A 1.02% 2646
1204 EMIM 2EHDTP 0.95% DITA 97.98% Aryl phosphate A 1.01% 2504 249
OMIM 2EHDTP 1.01% IONIC LIQUIDS EMIM 2EHDTP 100% 1108 OMIM 2EHDTP
100% 1400
* * * * *